Align desktop project modes and tray close behavior

[Luhaozhu]

Summary

Follow-up to merged PR #45 for the desktop 0.2.8 validation build.

• make project creation strictly follow the provisioned desktop mode: local-only exposes local projects, cloud-only exposes cloud projects, and dual mode exposes both
• apply the same guard to the CE-specific Projects page, chat project picker, and cloud project modal
• destroy the close-confirmation window after choosing minimize-to-tray so it cannot reappear
• allow both macOS architectures to build without Apple Developer credentials by using ad-hoc signing, while retaining Developer ID signing and notarization when the complete secret set is present
• bump all desktop manifests to 0.2.8 and document the behavior in English and Chinese

Root cause

The project creation controls previously assumed users could switch across deployment modes, while the CE-specific project-page overlay still exposed a generic cloud creation modal. The tray confirmation WebView was also retained after the main window was hidden, allowing its load handler to show it again.

For unsigned macOS builds, the runtime builder initially required APPLE_SIGNING_IDENTITY. After adding an ad-hoc fallback, tauri-action still received empty APPLE_CERTIFICATE variables and attempted to import an empty keychain certificate. The workflow now exports Apple variables only when the full signing and notarization secret set is available; otherwise it exports only APPLE_SIGNING_IDENTITY=-.

Validation

• CE derivation branding, pruning, resource, binary-asset, license, and release-regression gates passed
• desktop Node tests: 27 passed
• all desktop version references resolve to 0.2.8
• Desktop CI: passed (scripts plus Windows, Linux, macOS Apple Silicon, and macOS Intel offline cold starts)
• Desktop Release: passed on Windows x86_64, Linux x86_64, macOS Apple Silicon, and macOS Intel
• completed macOS logs explicitly report ad-hoc signing and successful upload of HugAgentOS_0.2.8_aarch64.dmg and HugAgentOS_0.2.8_x64.dmg
• the draft desktop-v0.2.8 release contains Windows NSIS, Linux AppImage/Deb, both macOS DMGs, updater archives, signatures, and latest.json

macOS installation note

The ad-hoc builds are intentionally not Apple-notarized. On first launch, users may need to open System Settings → Privacy & Security and choose Open Anyway. Adding the complete Apple secret set later automatically restores Developer ID signing and notarization without another workflow change.